(a) Field of the Invention
The present invention relates to a new imidazole compound, material for electronic device use, electroluminescent device, and electronic device; and more particularly, the new imidazole compound may be used as host material of a luminous layer of an electroluminescent device that makes up an organic electroluminescent device and material for electronic device use, electroluminescent devices containing the new imidazole compound, and electronic devices containing the material for electronic device use, including electroluminescent devices.
(b) Description of the Prior Art
Up to the present time, there are still many and varied discussions regarding the materials for electronic device use, especially luminescent materials and host materials of a luminous layer making up an organic electroluminescent device.
For example, Japan Patent Document 1 discloses using 2,4,5-triaryl to replace an imidazole compound and 1,2,4,5-tetra-aryl to replace an imidazole compound, the resulting compounds being used in blue fluorescence luminescent materials.
In addition, Japan Patent Document 2 discloses using benzylpyridine derivatives in luminescent materials, and using 2,4,5-tri(6-pyridyl biphenyl) imidazole derivatives to use as a phosphorescent host material.
Moreover, Japan Patent Document 3, in one aspect, discloses using imidazole having at least 1 or 2 electron withdrawing groups, and in another aspect, uses imidazole with electron donating groups, namely, producing a compound to use as a host material use.
Furthermore. Japan non-Patent Document 1 discloses using CBP (4,4,-N,N,-biz(carbazoly-9-yl) biphenyl) or mCP (1,3-di(carbazoly-9-yl) benzene) to use as a host material.
In addition, Japan non-Patent Document 2 discloses using benzodifuran derivative to use as a bipolar host material.
In luminescent devices using phosphorescence luminescent material to use as a luminescent material (dopant), the host material must have the full capacity to transport electrons and electron holes, as well as having good film-forming properties.
However, the stability of a thin film using the well known host compound CBP is inadequate. Moreover, mCP still has the problem of low thermal stability of the devices formed therefrom,
In addition, with a view to achieving high luminescence efficiency, in recent years, component structures are constructed from multilayer structures assembled from a great many layers. Hence, there is a need to reduce the number of layers of the component structure to enable simplifying the manufacturing process and reducing the costs. If an electroluminescent device uses benzodifuran derivatives as disclosed in Japan non-Patent Document 2, then an organic single layer or a reduction in the number of layers may be achieved. However, such a distinctive feature of the component structure makes manufacture difficult. Moreover, the film forming manufacturing process is restricted to using a vacuum evaporation method. And the manufacturing process still has the problem of being complicated. As for the present situation, simplification of the materials used in electronic devices is needed both in the component structure and the manufacturing process, nevertheless, up to the present time, no such materials have come to light.
In addition, with a view to achieving high luminescence efficiency, emphasis is first placed on the host material used, however, under the situation where the luminous layer of the host material has low stability, and with the trend moving toward the practicality of the driving stability of the electroluminescent device, problems still remain.